FACTORS AFFECTING DEVELOPMENT OF MUD-CRACKS 141 



the margin of the pan and separating the mud adhering to the side 

 from that on the bottom no regular mud-cracks developed until 

 a very late stage of* the desiccation. Instead of the usual familiar, 

 somewhat erratic, mud-crack lines seen on drying mud, a rive-rayed 

 star-shaped figure (see upper right-hand quarter of Fig. 6) cutting to 

 the bottom of the sediment first appeared. A day later two other 

 figures developed, each having three lines of equal length and form- 



Fig. 6. — Desiccated saline mud. The same quantity and kind of mud was used 

 as in Fig. 5 except that salt was added. Note that margins of polygons are curved 

 downward instead of upward as in the fresh-water mud-cracks shown in Figs. 1, 2, 3, 

 and 5. \ natural size. 



ing at their junction angles of 120 . Simultaneously with the 

 development of the three-line figures the entire surface became 

 marked by small hexagonal polygons with a diameter ranging from 

 I inch to T V inch and giving it a honeycomb appearance. These 

 may be seen indistinctly on the left half of Fig. 6. These were not 

 sharply defined nor marked off by mud-crack fissures, but were 

 discernible through a slightly lighter color of the sediment along 

 the bounding lines, and in some cases by a slight deliquescence of 



